It was weird. Even Paul Pierce seemed to acknowledge that. When you’re talking about a player who spent 15 years with the same team, seeing him hold up the jersey of a different color in a different city, weirdness is a guarantee.

“It’s really starting to sink in now that it’s become real,” Pierce said. “I’m no longer a Boston Celtic.”

The Celtics and Nets agreed to a trade back on draft night, one which sent Pierce to Brooklyn along with fellow star Kevin Garnett, plus guard Jason Terry. The teams were not able to complete the transaction, though, until the NBA’s July moratorium period was over. In the meantime, the trio of former Celtics was in limbo, waiting to become Brooklynites.

On Thursday, the Nets officially introduced the three, and the scene provided a stark contrast from the smiling, fawning press conferences that typically rules the day at this time of year.

It was obviously emotional for Pierce, who was drafted by Boston in 1998 and ranks second in Celtics history in scoring and third in games played. He acknowledged that he had always planned on ending his career in Boston, and still seemed somewhat stunned about the changes.

At one point, Pierce said, “It’s finally starting to become real. I’m no longer a Boston Celtic, I’m a Brooklyn Net. That’s what it is right now. It’s business. At some point, we all have to move on. I’m here to try and create some sort of legacy here in Brooklyn.”

The gathered crowd, which included season-ticket holders, cheered. Pierce did not so much as smile, though.

Still, overall, the situation in Brooklyn is mitigated by the fact that the Nets clearly have a chance at a championship, and that Pierce was able to make the change of scenery with Garnett alongside him.

It was Garnett’s arrival in Boston in 2007 that allowed Pierce, whose early years with Boston were turbulent, to play for a true championship contender for the first time in his career. The two forged a strong bond over the years.

Garnett, who had the ability to kill any deal because of a no-trade clause, said that the move of Terry and Pierce with him was, “a really, really, really big issue. I don’t know anyone who loves change, but change has to happen.”

They’re coming to accept that. But for Pierce, it’s still difficult. He is officially gone, and now he will have to work to help the Nets on their championship quest.

“We have no choice but to figure this out,” Pierce said, “and make this work.”